An automotive vehicle is configured to encourage a passenger to fasten a seatbelt by an alarm such as a buzzer when the passenger is seated on a vehicle seat but does not fasten the seatbelt nevertheless. When the passenger is seated on a passenger seat, an airbag is deployed in case of accident.
Therefore, the vehicle seat is provided with a load detection unit configured to detect a load of the passenger, and determines to be “seated” that means the passenger is seated when the load detected by the load detection unit exceeds a predetermined threshold set in advance, and determines to be “not seated” when the load is not higher than the predetermined value.
An example of a passenger sensing unit configured to determine the presence or absence of the passenger by sensing a load acting on the seat is described in JP 09-207638 A (hereinafter, referred to as Reference 1). In the passenger sensing unit disclosed in Reference 1, load sensors are installed only at two front and rear positions from among four seat mounting portions, whereby the presence or absence of the passenger is determined from the sum of the obtained two load values.
According to the passenger sensing unit described above, by mounting the load sensors at two positions at the front and the rear on the left or right side of the sensor mounting portion, the presence or absence of the passenger may be determined while minimizing the number of positions of installation of the load sensors, and achieving cost reduction and weight reduction of the unit.
However, in a configuration in which the load sensors are installed at two positions at the front and the rear on the left or right side of the seat mounting portion, the load to be detected by the load detection unit at the time of sudden turning of the vehicle is increased, and it may be erroneously recognized as being “seated” which indicates that the passenger is seated even when a light baggage is placed on the vehicle seat.
Accordingly, it is determined to be “passenger present” even though the passenger is not seated, an alarm of “seatbelt not fastened” is issued. Subsequently, when the load to be detected by the load detection unit is decreased with decrease in acceleration acting on the vehicle, the alarm of “seatbelt not fastened” is stopped. In this manner, an erroneous alarm which encourages fastening of the seatbelt may be repeated depending on the traveling state of the vehicle, which may give a driver a feeling of discomfort.
Therefore, a seatbelt warning apparatus configured so as not to be associated with drawbacks as described above is desired.